Proxy Auto-Config file is also known as PAC. Proxy Auto-Config file is a simple text file that contains a JavaScript function called “FindProxyForURL” . Proxy Auto-Config file or PAC is normally named as proxy.pac. Prxoy.pac file or Proxy Auto-Config file tells the internet browser to load its proxy configuration from a remote JavaScript file. In Proxy Auto-Config file (proxy.pac) we can specify different proxy to all URL’s. We can manually configure the URL of Proxy Auto-Config file or it is automatically created by Web Proxy Autodiscovery Protocol.
For detailed information about Proxy Auto-Config file (PAC) you can visit following links:-
http://en.wikipedia.org/wiki/Proxy_auto-config
http://wiki.daleroberts.info/doku.php?id=technical:automatic_proxy_configuration
